TDA7482 digital power amplifier circuit diagram

　　SGS-THOMSON has launched three single-chip Class D amplifier ICs, namely TDA7480 (10W), TDA7481C (18W) and TDA7482 (25W). This article takes the TDA7482 with the largest output power as an example.

　　TDA7482 is a Class D pulse width modulation monolithic power amplifier IC for audio. This series of ICs is mainly designed for high-efficiency applications such as the sound system of large-screen color TVs and home stereo devices.

　　The main technical parameters of TDA7482 are:

　　1. It has a rated output power of 25W. The working conditions are: RL = 4~8Ω, THD ≤ 10%. In fact, according to the recommended electrical parameters, when RL = 8Ω, Pout = 1W, its THD is only 0.1%.

　　2. High output efficiency. When Vcc=±21V, RL=8Ω, Pout=18W, the efficiency is 78%, so only a small heat sink is needed, or even no heat sink is needed.

　　3. Wide operating voltage range. The recommended value is ±10V~±25V, which is very suitable for car battery power supply.

　　4. There is an over-current protection device inside. When RL=0Ω, the protection action threshold is 3.5A~5A.

　　5. There is an overvoltage protection device inside, and the protection threshold is 50V.

　　6. With overheat overload protection, the overheat shutdown temperature is 150℃.

　　7. With ST-BY and MUTE functions.

　　8. The recommended carrier operating frequency of pulse width modulation is 100kHz~200kHz.

　　9. Input noise (20Hz~20kHz) is 7μF~12μF.

　　10. Input impedance is 30kΩ.

　　11.Maximum power consumption 3.8W.

　　The typical application circuit of TDA7482 is shown in the figure below

　　In the past half century, foreign magazines have continuously discussed and reported on pulse width modulated Class D audio amplifiers. The main attractive feature of this technology is its high output efficiency (generally over 85-90%), which is more important for amplifiers with larger output power. However, its distortion index is still far from the Hi-Fi requirements. At present, the THD of all known Class D PWM amplifiers is about 0.1%-0.01%, but it is difficult to reach this range when the power is greater than 50W. Although the audio amplifier made with PWM does not feel very musical. Secondly, the strong PWM carrier frequency will inevitably cause serious electromagnetic interference in the medium and short wave bands, which is probably a problem that the existing filter design cannot satisfactorily solve. Nevertheless, in the audio output stage of large-screen color TVs, the audio part of multimedia computers and car stereo systems, the above shortcomings of PWM amplifiers do not seem to be important, so they have found their uses. Moreover, international large companies such as SGS-THOMSON have launched such series of chips in a single-chip form, and it can be expected that they will work very reliably, so they are worth recommending.